The present invention relates to an insulated electrode used during surgical procedures and a method of assembling an insulated electrode. The present invention particularly relates to electrode insulators and methods of insulating an electrode that reduce meltback of the insulation and the incidence of scope damage due to high temperatures generated during the cutting or coagulation cycle.
Resectoscopes are commonly used to cut and coagulate tissue of a patient during a surgical procedure. The typical resectoscope includes an optical component for illuminating and viewing a target tissue, valves for controlling irrigating fluids, an active element, such as a loop electrode, for cutting tissue and sealing blood vessels, and a handle assembly for connecting electrosurgical current from a generator to the loop electrode. During the surgical procedure, radio frequency (RF) electrical energy passes through the electrode, into the target tissue and causes heating of the target tissue. The amount of heat applied to the tissue controls the cutting and coagulation process.
An example of a surgical procedure utilizing a resectoscope is transurethral resection of the prostate (TURP). TURP is used to treat benign prostatic hyperplasia (BPH), a medical condition causing urinary tract obstruction commonly experienced by men over fifty years old. During the surgical procedure, the surgeon uses a loop electrode to remove the obstructing tissue one piece at a time. Tissue pieces are washed into the bladder using irrigating fluids and subsequently flushed out at the end of the procedure. Various instruments for performing surgical cutting and coagulation procedures such as TURP are known in the art.
An example of such a device may be found in U.S. Pat. No. 5,658,280, which discloses an electrode assembly for a resectoscope. The electrode assembly includes a cutting electrode and a coagulation electrode, with insulation surrounding at least a portion of both the cutting and coagulation electrodes. A support frame connects the cutting and coagulation electrodes to an energy source for supplying energy to the electrodes. The coagulation electrode provides tissue coagulation simultaneously while the cutting electrode cuts tissue.
A further example may be found in U.S. Pat. No. 5,702,387, which discloses an electrosurgical electrode which resists buildup of eschar. The electrode includes a coating of silicone elastomer, applied by dipping, molding or electrostatically spraying the silicone onto the electrode, which improves the ease of cleaning any tissue buildup, such as eschar. The coating is thin or nonexistent at the electrode blade edges and tip. A function of this particular silicone coating configuration is to concentrate the current at the edges and tip of the electrode, resulting in improved eschar removal.
Yet still a further example is found in U.S. Pat. No. 5,810,764, which discloses an electrosurgical probe with an active electrode coupled to a high frequency voltage source. In one aspect of the invention, the active electrode includes a xe2x80x9cnon-activexe2x80x9d portion or surface that selectively reduces undesirable current flow from the non-active portion into tissue or surrounding electrically conducting liquids. The xe2x80x9cnon-activexe2x80x9d electrode portion is coated with an electrically insulating material which is applied to the electrode by plasma deposition, evaporative or sputtering techniques, or dip coating processes.
The above-described electrodes used. during an electrosurgical procedure (and other similar devices not specifically described) offer many advantages to potential users, including effectiveness, safety and convenience. However, it has been discovered that an obstacle or disadvantage to such devices is the susceptibility to meltback of currently used insulation materials and insulation designs. This is due to a variety of factors, including high temperatures generated during the cutting cycle. When the insulation is compromised due to meltback, there is the likelihood that the adjoining components of the resectoscope may also be damaged by the high temperatures. Further, the additional exposed surface area of the active portion of the electrode may destroy surrounding non-target tissue and cause patient injury.
There are a number of causes of current meltback problems. For example, insulators made from Fluoronated Ethylene Propylene (FEP) or Tetra Fluoro Ethylene (TFE) do not closely conform to the external diameter of the electrode wire and therefore lead to concentrated contact points which, due to the somewhat low melting point of FEP and TFE, makes. these contact points more susceptible to meltdown. In addition, the insulators such as sputtered silicone coatings similarly do not provide the uniformity of insulation, thus leading to uneven heat concentration. Moreover, the sputtering process is expensive and difficult to perform reliably.
In view of the above, it is apparent that there is a need to provide an electrode such as those described above with a more durable and reliable insulation element and insulator design that can withstand the range of temperatures generated during an electrosurgical procedure. There is also a need to provide a method of manufacturing such an improved insulator that is efficient, easy to implement and cost effective. Such insulation characteristics include electrical insulation resistance to meltback and efficient manufacturability to ensure the device is biocompatible and non-toxic so as to prevent adverse reactions in both patients and users of the device. It further includes properties that reduce the incidence of scope damage caused by electrical discharge and the intensity of heat generated during the cutting and coagulation cycles.
In view of the foregoing, it is an object of the present invention to provide an insulated electrode assembly that addresses the. obstacles and disadvantages associated with the current problems of insulation meltback and inadvertent electrical discharge due to a variety of factors, including generation of high temperatures and arcing to the resectoscope during surgical procedures.
A further object of the present invention is to provide an insulated electrode assembly that reduces the incidence of scope damage due to the high temperatures generated during cutting and coagulation cycles and inadvertent electrical discharge caused by arcing to the resectoscope.
A further object of the present invention is to provide an insulated electrode assembly that reduces insulation meltback caused by high heat intensities.
A further object of the present invention is to provide an insulated electrode assembly that prevents the destruction of surrounding non-target tissue and reduces potential patient injury.
A further object of the present invention is to provide an insulated electrode assembly that includes uniform insulation thickness and surface contact between the insulation and the electrode.
These and other objects not specifically enumerated herein are believed to be addressed by the present invention which contemplates an electrode assembly that includes an elongated wire and an insulation tube located on a portion of the wire, wherein the insulation tube in an undeformed state may have an internal diameter smaller than the external diameter of the elongated wire. The insulation tube or element that is disposed on the active portion of the electrode forms a non-active section.
The present invention also contemplates a method of assembling insulation onto an electrode which may include the steps of sliding one end of an insulation tube over an assembly tool tip and securing the insulation tube to the tool. The next steps may include positioning one end of the electrode into the other end of the insulation tube and introducing a flow of fluid through the insulation tube. The following step would include inserting the electrode into the insulation tube during the flow of fluid causing the insulation tube to float over the electrode. The final step would likely include discontinuing the flow of fluid so that the insulation surface uniformly contacts the electrode.